The present invention relates to apparatus for transporting sheet- or plate-like commodities, particularly for transporting stacks of paper sheets between one or more first stations and one or more second stations. For example, the apparatus of the present invention can be utilized to transport stacks of paper sheets from one or more machines which convert large sheets or rolls of paper into stacks of legal size or letter size and one or more packing machines wherein the stacks are introduced into cartons or other types of receptacles.
Stacks of superimposed paper sheets must be transported in such a way that their sheets remain in positions of accurate alignment with one another. This is a prerequisite for predictable introduction of stacks into properly dimensioned cartons or other types of receptacles (as a rule, the dimensions of such receptacles barely suffice to permit insertion of stacks of paper sheets). Thus, it is necessary to avoid abrupt acceleration or deceleration of stacks and/or their conveyors during transport from the stacking station to the packing station. It is also desirable and advantageous to avoid the application of pronounced shocks and/or abrupt changes in the direction of transport because all such influences can adversely affect the configuration of stacks which arrive at the packing station. Careful transport of stacked paper sheets is even more important in modern high-speed paper processing plants wherein each packing machine must pack a large number of stacks per unit of time so that there is no time left for realignment of sheets in a stack prior to introduction into a receptacle.
In many presently known plants for the processing of sheets of paper or other sheet material, stacks of paper sheets or other sheet-like commodities are transported by elongated transporting units each of which normally comprises a first or supplying conveyor serving to accept stacked sheets from a stacking or other stack-feeding or stack-storing unit, an intermediate conveyor which receives successive stacks or groups of stacks from the supplying conveyor, and a third or receiving conveyor which accepts the stacks or groups of stacks from the intermediate conveyor. The receiving conveyor can deliver stacks or groups of stacks directly to a packing machine or to one or more further conveyors which serve to deliver stacks or groups of stacks to one or more packing machines. As a rule, each such conveyor comprises a table-like frame and an endless belt or band which is recessed into the frame and whose flat upper reach is flush with the upper side of the frame. A large paper processing plant will comprise a large number of magazines for discrete stacks or groups of stacks, an equal number of packing machines, and a discrete multi-conveyor transporting unit for each packing machine. Such plants exhibit the drawback that their machines are not used to capacity under any and all circumstances which develop in actual operation. For example, it is often necessary to operate a packing machine at less than full capacity at which time a single transporting unit suffices to deliver stacks at a requisite frequency. However, such single transporting unit is incapable of satisfying the needs of a high-speed packing machine when the latter is operated at or close to maximum capacity.
It is already known, in fields of endeavor other than processing of stacked paper sheets or the like, to convert plural transporting units into a larger-capacity transporting unit or vice versa. As a rule, the plural transporting units are designed to advance commodities in different directions. Such transporting units cannot be used for the transport of unconfined stacks of paper sheets or the like because they would be incapable of delivering stacks to their destination without at least some shifting of neighboring sheets or without at least some shifting of lowermost sheets with reference to their supports, especially if they were to be operated at a speed which is required in a modern paper processing plant.